1. Field of the Invention
The present invention relates to an intake system for an internal combustion engine which is to be applied to a motorcycle or other vehicles.
2. Description of Background Art
An intake system for an internal combustion engine which is to be applied to a motorcycle or the like is known wherein a structure is provided in which a contrivance is made to cope with leakage of blow-by oil and/or fuel through a fastened portion between an air cleaner case and a throttle body. See, for example, Japanese Patent Laid-Open No. 2010-59894.
Japanese Patent Laid-Open No. 2010-59894 discloses a structure of a motorcycle which includes a throttle body having an air passage to permit a flow of air to an engine; a cleaner box (air cleaner case) joined to the throttle body and conducting clean air into the throttle body; screws for fastening the cleaner box and the throttle body to each other on the outside of a left-side air passage and a right-side air passage of the air passage; and a seal portion for sealing the joined portion between the cleaner box and the throttle body, wherein the seal portion is disposed so as to surround the outside of the screw fastening positions, the left-side air passage and the right-side air passage.
By this structure, exudation of blow-by oil and/or fuel through the fastened portion between the cleaner box and the throttle body is restrained.
In the structure as disclosed in Japanese Patent Laid-Open No. 2010-59894, there is provided a function to prevent blow-by oil and/or fuel from exuding via the joined portion between the throttle body and the cleaner box. In addition, it is possible to prevent the outer surfaces of the engine from being contaminated by engine oil and/or fuel.
However, since the sealing between the throttle body and a funnel is made at a funnel extension portion (the lower end portion of the funnel which is to be inserted into the throttle body), the dimensions of the funnel extension portion are specified rigorously, leading to troublesome tolerance control at the time of manufacture.